Where Did This Coronavirus Originate? Virus Hunters Find Genetic Clues In Bats
MADDIE SOFIA, HOST:
You're listening to SHORT WAVE from NPR.
LINFA WANG: Sorry. I have an important message people just sent to me. I have to type.
EMILY KWONG, HOST:
OK. OK, please.
WANG: We're in a war zone right now, so everything comes to me very fast, and they want an answer.
KWONG: So, Maddie, this is Dr. Linfa Wang. I reached him in Singapore. He and his team have been working around-the-clock to help that country fight this coronavirus. He hasn't hugged his daughter in over two months, and he's been interviewed over a hundred times.
WANG: BBC, Sky News, you know, CNN, you know, ABC.
KWONG: NPR's Morning Edition.
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NOEL KING: Dr. Linfa Wang is a virologist at the Duke-National University of Singapore. He joins me on Skype. Doctor, thanks for being here.
WANG: Thank you for having me.
SOFIA: What up, Noel King?
KWONG: That's right. And the reason Linfa is so sought after right now is because he's a leading expert on emerging zoonotic diseases, or diseases hosted in animals that spread to humans.
SOFIA: Right, things like Lyme disease, West Nile and, of course, diseases caused by emerging coronaviruses like the one we're dealing with right now.
KWONG: That's right. The CDC estimates that 6 out of 10 infectious diseases in people come from animals. And I know you told SHORT WAVE listeners that we would not talk about the Hollywood movie "Contagion."
SOFIA: Come on, Kwong. A promise is a promise.
KWONG: OK, but hear me out. "Contagion" - it's a good framework for talking about where this coronavirus came from. The movie is also about a zoonotic pandemic, and it makes brief mention of Linfa's work 30 minutes in, in a conversation between two very upset CDC officials.
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LAURENCE FISHBURNE: (As Dr. Ellis Cheever) He grew it.
JENNIFER EHLE: (As Dr. Ally Hextall) He tried antibodies and immunological MAC outlines like we did, but the key was a fetal bat cell line from Geelong. We didn't have it.
KWONG: Did you hear that line about fetal bat cells?
SOFIA: I did.
KWONG: Well, the screenwriters were actually referencing Linfa's work with bat-borne diseases because after the 2003 outbreak of SARS, which was a brand-new coronavirus then...
SOFIA: But something we call SARS classic or original SARS now.
KWONG: Yes. Linfa was one of the many people that helped solve the mystery of where SARS came from, tracing it to horseshoe bats in a cave in the Yunnan province of China. It was a detective hunt that took a decade, sampling thousands of horseshoe bats across the country. We're talking about poking around in fresh guano, which is bat poop, and seeing if it's a genetic match to the virus.
WANG: You have to be there at the right time, right place. You know, bats are not going to just, you know, give you the virus. So we wait. You know, we sample their fecal samples, urine and, you know, blood.
SOFIA: Ah, yes, the glory of fieldwork.
KWONG: And this is the work of virus hunting. It actually took scientists 10 years to track SARS to that cave in Yunnan. They knew bats were the likely host for the virus, but which bats and from where took time. And the same thing applies to this coronavirus. We're pretty sure bats are the hosts, too. But how it moved from bats to people will also take time to figure out.
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WANG: Of course, the technology and everything is much more advanced 17 years later. But I think that for us to, you know, try to solve everything in two to three months is just not feasible. And also, in science, I say that, always, a little bit of luck is required.
SOFIA: I'm Maddie Sofia.
KWONG: And I'm Emily Kwong.
SOFIA: Today on the show, virus hunting - what scientists know and don't know about the true origins of this coronavirus.
KWONG: And why figuring out where it came from is so important for preventing future outbreaks.
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SOFIA: All right, Emily Kwong, SHORT WAVE reporter, animal lover.
KWONG: Unabashed animal lover - it's true.
SOFIA: You and I both know that bats are amazing. That is not up for dispute on SHORT WAVE. They're important for pollinating flowers, dispersing seeds. They catch bugs - the same ones that bite us and eat up some of our crops. But bats also harbor some of the toughest known zoonotic diseases.
KWONG: That's right - the rabies virus, the Marburg virus, the Hendra and Nipah viruses. The Ebola virus outbreak in West Africa was traced to a bat colony. All these viruses find what's called a natural reservoir in bats, meaning the viruses live in that host without harming it.
SOFIA: Do we know why that is?
KWONG: It's a very interesting question.
WANG: Yeah. So I used to say it's a million-dollar question. Now I say it's a billion-dollar question.
KWONG: Linfa Wang says it might have to do with the fact that bats are the only mammal that's adapted for flight.
WANG: Because during flight, their body temperature goes to, like, up to all the way to 42 degrees.
SOFIA: That's super high. Forty-two degrees Celsius is almost 108 degrees Fahrenheit.
KWONG: And their heartbeat goes up to a thousand beats per minute. They're burning a ton of energy flying several hours a day. And this creates toxic free radicals that damage their cells. But Linfa's research has shown that bats have also evolved this ability to repair and minimize that cellular damage, kind of a counterstrike. And those same defensive abilities may help them not only tolerate flight but also to fight infectious diseases in a way that the human body simply cannot.
SOFIA: So they essentially have this, like, super effective immune response.
KWONG: Right. So while our immune systems can get overwhelmed from fending off these viruses, he thinks bats don't.
WANG: Our hypothesis is that bats has evolved a different mechanism to get the balance right for defensive tolerance, and that favors the virus to live peacefully with bats.
KWONG: And they're able to safely house these viruses in their bodies and not get sick from them.
SOFIA: Got it. So let's talk about why scientists think this particular coronavirus could've come from bats.
KWONG: Well, they got a big clue from the start. So in early January, Chinese scientists were able to quickly sequence the virus' entire genome, and then they published it online. From that, scientists could begin to study the virus in depth.
SOFIA: And around this time, researchers at the Wuhan Institute of Virology in China compared its genome to a library of known viruses, right? And it found a 96% match with coronavirus samples taken from horseshoe bats in Yunnan.
KWONG: Yes, the same kinds of bats that were natural reservoirs for the original SARS virus that broke out in 2003. And this led them to believe that this new coronavirus likely came from bats, too.
SOFIA: Right. And from a genetic standpoint, a 96% match sounds like a lot, but that 4% can make a big difference.
ROBERT GARRY: But that 4% difference is actually a pretty wide distance in evolutionary time. It could be even decades.
KWONG: This is Robert Garry, a virologist at Tulane University. And while that one paper says there's a 96% match with bats, that extra 4%, to him, suggests some other viral material may have gotten mixed in from another animal. And that other animal could have even transmitted the virus to humans.
SOFIA: Right. This is called an intermediate host, or an in-between host.
KWONG: Correct. But when it comes to this coronavirus, scientists aren't sure if there was an intermediate host between bats and humans. And if so, they're not sure what the intermediate host could be. There are theories. Robert and fellow researchers have hypothesized this coronavirus could be a blend of viruses from two different animals, bats and something else. And early scientific studies suggest it could be this animal called a pangolin, this scaly anteater vulnerable to illegal wildlife trade.
GARRY: And a virus of pangolins or some other animal that has this similar receptor-binding domain. So two viruses getting together, recombining to make the new SARS-CoV-2.
KWONG: But the important point to all this is that virus hunters haven't come to a definitive conclusion about the chain of transmission from animals to humans, about the involvement of pangolins and bats or any other host animal - not on the level of proof they need.
SOFIA: Right, like the genetic level.
KWONG: Yes, we don't know definitively which animal or animals this came from. It will take time to figure out. But we do know this came from animals. A bunch of scientists in mid-February published this big letter in the journal Lancet saying evidence overwhelmingly points to wildlife as the origin for this coronavirus. And Robert stands by that, too.
GARRY: I can tell you that this is a product of nature. It's not a virus that has arisen in the laboratory by any scientist purposefully manipulating something that was then released onto the public. That just didn't happen.
KWONG: Because if you look at the actual genome, which Robert has done, the evidence isn't there.
SOFIA: OK. So you said earlier while speaking to the researcher in Singapore that it took a decade to find out the actual origin of the virus that caused SARS - the original SARS. Do we know how long it could take to figure out where this new coronavirus came from?
KWONG: Oh, Maddie, I wish I had an answer for you. We don't. It all depends on funding and resources...
SOFIA: Doesn't it all, Kwong?
KWONG: ...And time. Like I keep saying throughout this whole episode, investment in virus hunting - right? - expanding these zoonotic studies to figure out the transmission chain between animals and people. Because if we know that, we are armed with information that can help us prevent future outbreaks.
Peter Daszak - he's the president of the U.S.-based nonprofit EcoHealth Alliance, and he says that even if bats are the likely origin, they are not to blame.
PETER DASZAK: It's not bats. It's us. It's what we do to bats that drives this pandemic risk.
KWONG: Like wildlife trade and food and agriculture practices or our close proximity to animals in densely populated areas.
DASZAK: You know, one of the positive things about finding out that we're actually behind these pandemics is that that gives us the power to do something about it. We don't need to get rid of bats. We don't need to do anything with bats. We've just got to leave them alone. Let them get on doing the good they do, flitting around at night, and we will not catch their viruses.
KWONG: The 2003 SARS outbreak may have taken the world by surprise, but a pandemic of this proportion was anticipated by scientists.
SOFIA: Oh, yeah. For sure. I mean, the way that the virologists I went to school with kind of talked about it was like it's not an if; it's a when.
KWONG: Yeah. That's really interesting, given that infectious diseases, including those from animals, have been on the rise for decades. Linfa Wang, the virologist in Singapore, is actually kind of heartbroken by the fact that countries around the world failed to understand the impact this would have early on.
WANG: I'm so angry right now because I said that this COVID-19 outbreak - before January 20, it's the Chinese fault - the Chinese government, Chinese authority, whatever. But after January 20, the rest of the world is still not taking it seriously, right? You know, our political system, our diplomatic system and our - whatever - international relationship system is just not ready.
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KWONG: January 20, by the way, is when Chinese health officials confirmed the new coronavirus could be transmitted between humans, and it's when the World Health Organization kicked into high gear to evaluate the global risk. At that point, there were more than 200 cases, and we're now nearing 2 million confirmed cases worldwide as of this recording.
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SOFIA: All right, Emily Kwong, I appreciate you. Thank you for reporting this out.
KWONG: Sure thing.
SOFIA: This episode was produced by Brit Hanson, edited by Viet Le and fact-checked by Emily Vaughn. I'm your host, Maddie Sofia.
KWONG: I'm your reporter, Emily Kwong.
SOFIA: Thanks for listening to SHORT WAVE from NPR.
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